Roots blowers make great vacuum pumps as well. We have about 10 of them at work every day in the molding shop where I work. Noisy and hot, but long lasting! Dan
Roots blower is made up of two (or more) very close fitting screws that are gear or pulley driven from the crankshaft. Turbo is normally driven entirely by the exhaust gases leaving the engine. The exception to this rule appears on the Electromotive Diesels from General Motors. These engines have a Turbo that is also gear driven. The Gear drive comes from the cam shaft and spins the turbo, as the engine exhaust becomes more powerful, the exhaust starts to push the turbo, such that at ~95% of full load the turbo is completely driven by the exhaust gas. An overrunning clutch is used to disengage the turbo from the gear drive. To my knowledge this is a very limited application. Most likely driven by the need for a blower on a 2 cycle diesel and the desire for more a more efficient, more powerful engine at full load.
